1. Field of the Invention
The present invention relates to an apparatus and a method for detecting interference in a heterogeneous system of a mobile communication system that uses an Industrial, Scientific and Medical (ISM) band. More particularly, the present invention relates to an apparatus and a method for determining a start section and an end section of a packet using an Automatic Gain Control (AGC) change in a Zigbee communication system that uses an ISM band and detecting interference in a heterogeneous system using a reception rate of a packet and an interference occurrence rate depending on whether a synchronization process is performed during the determined section.
2. Description of the Related Art
Recently, as mobile communication develops rapidly, particularly a mobile terminal that enables wireless voice communication and information exchange has become a necessity. In an early stage of a mobile terminal, the mobile terminal has been simply recognized as a terminal that can be carried with and enables wireless communication, but as a technology of the mobile terminal develops and a wireless Internet is introduced, the mobile terminal is not only used for the purpose of simple telephone communication and schedule management, but also expands its utilization range such as capturing an image using a built-in camera, viewing satellite broadcasting, games, and a remote controller using short distance communication.
The short distance communication of the above described functions is a function of providing an advantage of being able to communicate with a peripheral apparatus. A manufacturer of a mobile terminal brings a mobile terminal that includes a short distance communication function such as Bluetooth, Zigbee, Ultra-Wideband (UWB), Wireless Local Area Network (WLAN), Rubee, and the like, to the market.
The Zigbee of the above-described short distance communication technologies is a communication scheme that uses an ISM band, and can provide a data speed of 250 kbps at the maximum and can configure a network of 65,535 sensors at the maximum.
However, since the Zigbee communication uses the ISM band, a communication problem by interference by a heterogeneous system, for example, a wireless LAN or Bluetooth may be generated. Therefore, Zigbee communication needs to select a frequency channel where interference is relatively small in order to guarantee stable data transmission/reception. At this point, the mobile terminal determines a channel where interference is small through the following interference component detecting method.
A first method determines that interference exists when a Received Signal Strength Indication (RSSI) level of a reception signal exceeds a specific threshold. A second method determines that Zigbee signals exist in a frequency channel currently in use when a start-of-frame delimiter (SFD) of a Zigbee packet is received even though RSSI does not exceed a threshold. A last method of detecting an interference component determines that Zigbee signals exist in a frequency channel currently in use when RSSI exceeds a threshold and an SFD is received.
However, of the above methods, the RSSI measuring method cannot determine whether a heterogeneous system besides a Zigbee system exists in a current channel, and the method of determining whether a Zigbee packet exists has a problem of having to constantly maintaining an operation for receiving the packet, that is, a reception mode state.